Various implementations have been made in the industry to extend the bus architecture of computer systems to additional chassis. This was first widely implemented in the early 1980's as PC expansion chassis were commercialized by IBM and others. These systems extended the processor bus by inserting a card in one processor slot of each system and then interconnecting the systems by a cabling configuration between the inserted cards. This solution was satisfactory with the relatively slow systems of the time. A more recent example is Dialogic Corporation's ScxBus extender. This implementation takes signals from a time division multiplexed bus and retransmits them over a SCSI-like cable and connector system. This system is very costly and the distance the system can be extended is limited due to timing and loss considerations. Cabling approaches such as these that connect separate chassis or slot sets in a cabinet disrupt the timing and electrical characteristics of the resultant extended bus.
A system's capabilities can also be extended by transmitting bus information to another system's bus over a LAN using protocols such as Ethernet, ATM, or other packet protocol technologies. This also is an expensive solution, and introduces relatively long delays in the bus traffic.
Another solution to expanding an existing system within a cabinet is to replace the backplane with one that has sufficient slots for the application at hand. Not only is this solution expensive, but it is labor intensive and tends to be disruptive to the system.
Accordingly, it is an object of the present invention to provide an inexpensive solution to easily extend the expansion slots and buses of a system within a cabinet while minimizing the impact to system timing and electrical characteristics.
Another object of the present invention is to extend the expansion slots and buses of a system within a cabinet without modification or replacement of the backplane.